At the present time, electropneumatic controllers that employ compressible fluids to drive the manipulator limb are known in the art. Pneumatic manipulator limbs may be used for quite a number of applications including air brakes, control of robot-like motion, control of material handling equipment, arms and grippers and the control of limbs for walking machines. Representative pneumatically powered robotic apparatus are disclosed in U. S. Pat. No. 4,379,335 to Kirsch, et al., U. S. Pat. No. 3,476,266 to Devol and U.S. Pat. No. 4,339,984 to Huhne.
Of interest, Kirsch, et al. discloses an electronic control system for a pneumatically powered point-to-point robot. The robot movement is controlled by an electronic control system including a portable programmer and electronic controller which control solenoid valves associated with air flow to the robot. Mechanical stops are utilized to set the parameters of movement of the robot required for a particular application. Devol discloses a binary-code controlled pneumatic robotic apparatus wherein the control apparatus transmits binary-code instructions to the solenoid valve to control air flow and consequent robotic movement. A hydraulic brake is utilized to prevent erratic operation of the pneumatic robotic apparatus during a change in the actuation of fluid-pressure actuators from one combination to another so as to effect a change in robotic movement. Also of interest, Huhne discloses a drive for an industrial manipulator utilizing compressed air to and from a double-acting air cylinder through a solenoid valve arrangement controlled by an electronic control unit. An electromagnetic brake is also controlled by the electronic control unit in order to stop movement of the manipulator at a desired final position in an orderly fashion.
Although previously known pneumatic manipulator control systems have recognized the problem of accurate manipulation of a control limb and the necessity to accurately stop the manipulator or limb at the end of its predetermined movement from a first to a second position, it is not believed that the problem has been fully and adequately dealt with to date. Overshoot by a pneumatic limb of a predetermined stop point and/or oscillation around the stop point by the pneumatic manipulator or limb continues to be a problem in the pneumatically controlled manipulator field. As can be appreciated, the more complex the movement of the pneumatically controlled limb, the more difficult becomes the problem of stopping the movement at a predetermined point in an orderly fashion. Applicant has found a novel and highly effective system by which to affect rapid movement of a pneumatically controlled flexible limb without resulting in overshoot or oscillation about the end point of movement. This system is believed to be a significant advance in the field of pneumatically controlled flexible manipulator limbs.